1. Field of the Invention
The present invention relates to a method for manufacturing a water repellent member in which the surface of a substrate made of glass, ceramics, plastic, metal, or the like is covered with a film having water repellent properties, and also relates to a method for manufacturing an inkjet head.
2. Related Background Art
Heretofore, various kinds of water repellent preparations and methods have been developed and used for providing various products such as industrial equipments and electronic equipments with water repellencies, weather resistances, antifouling property, and so on.
In order to keep such surface characteristics, the following three methods have been used.
A first method is one by which the surface of a substrate made of glass, plastic, metal, or the like is roughened by blasting or etching, treated with a primer or the like, and coated with a paint containing fluorine-contained resin such as polytetrafluoroethylene (PTFE), followed by baking at a temperature of 350 to 400xc2x0 C. after drying to apply the fluorine-contained resin on the surface of the substrate.
A second method is one comprising the step of forming a fluororesin such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene-hexafluoropropylene copolymer on a substrate made of glass, plastic, metal, or the like by a vacuum evaporation method, a spattering method, or the like.
A third method is one that forms a water repellent metallic compound material obtained by dispersing polytetrafluoroethylene oligomer having a molecular weight of about 8000 to 10000 in a plating solution and then co-depositing the oligomer on a plated film as disclosed in JP-A-4-283268.
In each of these methods, a high water repellent substance is coated on the surface of a substrate to provide the substrate with surface properties such as water repellent properties. However, it is also known that the water repellent properties are not only depended on the water repellent properties of the coating material but also depending on the surface condition of the substrate.
Therefore, for attaining higher water repellent properties, an attempt has been made to increase an apparent surface area of the water repellent surface more than the actual surface area thereof by forming minute raised portions on the water repellent surface.
In JP-A-4-239633, for example, there is disclosed a method of forming a water repellent film having a rough surface by chemically bonding between a layer having microscopic asperities prepared by blending fine particles with silicate glass particles and a polymer film layer having a fluorocarbon group and a siloxane group by a siloxane bond.
However, the resulting fluororesin coating film has a poor resistance to scuffling in spite of having excellent water repellent properties, so that it cannot be used as a hard coating film.
For solving such a problem, JP-A-3-153859 discloses a coating film as a water repellent film having the resistance to scuffling. The coating film comprises an undercoating layer made of a metal oxide formed on a plastic substrate and a layer of a mixture of a metal oxide and a fluororesin formed on the undercoating layer.
In JP-A-3-153859, such a coating film is formed by the process vacuum deposition of a metal oxide as an undercoating layer on a plastic substrate and the process of spattering using a target comprised of the metal oxide and a fluororesin to form a coating film provided as a mixed layer of the metal oxide and the fluorocarbon.
However, the conventional technologies described above have the following disadvantages.
In the conventional first method, there is a need to prepare a paint including particles that contain a fluororesin such as polytetrafluoroethylene (PTFE). In addition, the process has to include steps of coating, drying, and baking. Consequently, the process becomes complicated.
The third method prepares a water repellent metallic compound material obtained by dispersing polytetrafluoroethylene oligomer having a molecular weight of about 8000 to 10000 in a plating solution and then co-depositing the oligomer on a plated film. In this method, however, there is a need to disperse the polytetrafluoroethylene oligomer in the plating solution.
Therefore, the third method has a limited selection of raw materials.
In each of the conventional first, second, and third methods, furthermore, the coating film is covered with a single fluororesin layer, so that it has an excellent water repellent property but poor in the resistance to scuffing.
For obtaining a coating film having an excellent resistance to scuffing, as described above, there is a method in which a metal oxide layer is provided as an undercoating layer on a substrate and a layer of a mixture of a metal oxide and a fluororesin is formed on the undercoating layer. In this method, at the time of forming the coating layer from the mixed layer of the metal oxide and the fluororesin by the sputtering method using a target comprised of the metal oxide and the fluororesin, for sputtering the fluororesin and the metal oxide with the same amount of the charged electric power, in general, the sputtering of the fluororesin having a film-forming rate compared with that of the metal oxide is selectively performed. Therefore, it is difficult to control the composition of the mixed layer (the contents of the metal oxide and the fluororesin in the coating film) is difficult, so that the water repellent properties and the resistance to scuffing are hardly rose to a desired level.
Therefore, it has been desired to provide a method for easily forming a coating film having water repellent properties and resistance to scuffing in excess of a certain level.
An object of the present invention is to provide a method for manufacturing a water repellent member covered with a water repellent film having an excellent water repellent property and an excellent durability, where such a water repellent film is formed on only a desired surface by a simple process without including complicated steps of masking and so on and also without restricting on the selection of raw materials.
Another object of the present invention is to provide a method for manufacturing an inkjet head having orifice plates with improved ink-repellent properties.
A first aspect of the present invention is a method for manufacturing a water repellent member having a substrate and a water repellent film covering the surface of the substrate, comprising the steps of: transporting particles of a water repellent material with a gas; and discharging the transported particles from a nozzle to the substrate to form the water repellent film on the surface of the substrate.
A second aspect of the present invention is a method for manufacturing an inkjet head equipped with an orifice plate having a ink-repellent surface, wherein the formation of the orifice plate includes the steps of: transporting particles of a ink-repellent material with a gas; and discharging the transported particles from a nozzle to the substrate to form the ink-repellent film on the surface of the substrate.